While trying to reduce the overall noise level on some boards I’ve been working with, I was looking for a reliable way to first measure the noise level and figure out how best to address the problem.  If you can’t measure or visualize it, it’s hard to fully understand it and reliably fix it!   Looking for a solution to measure the quality of the GND planes, etc., I came across this helpful appnote from Analog Devices: Measuring Ground Noise.  They present a relatively straight-forward setup based on an AD620 instrumentation amplifier that can be used to characterize the GND plane on your boards.  The article is worth reading simply because it brings up something a lot of people don’t think about doing boards design: GND.  Particularly with high-speed design (anything greater than a few MHz), or with switching-mode power supplies, etc.,  it’s important to think about the return paths on your boards in addition to the signal transmission lines and part placement.  Howard Johnson’s High Speed Digital Design is probably the best book (that I know of!) on the subject, but I haven’t seen very many circuits showing how you can measure noise on the gnd plane, so I thought it was worth sharing the above PDF.

I’ve been doing a lot of power supply testing lately, using both switching a linear supplies.  Since it’s not something I’ve had to do often in the past (I’m an apps person, not so much a test engineer) … I thought it was worthwhile to spend a bit of time digging around for app notes on accurately characterising linear and switching supplies.  Long story short: AN 372-1 from Agilent was one of the more useful ones I found (though I’m sure there are dozens out there). Short story long: read on … (more…)

Having a hard time trying to figure out whether that FET can handle enough current for your project?  AN11158 from NXP might help clarify some of the many parameters that you need to take into account that are often overlooked.  The Safe operating area, for example, is an important one that often gets skipped and people just look at the best-case scenario marketing numbers on the front page of the datasheet: “The Safe Operating Area (SOA) curves are some of the most important on the data sheet. The SOA curves show the voltage allowed, the current and time envelope of operation for the MOSFET. These values are for an initial Tmb of 25°C and a single current pulse. This is a complex subject which is further discussed in the appendix (Section 3.1).”

It’s pretty rare that I come across a free book with so much good information in it, but Analog SEEKrets is definately worth a few days of any budding young engineers time.  Written by someone who clearly has enough years experience behind them to know what they’re talking about, this book — freely downloadable in PDF format — contains a lot of excellent real-world information that anyone working in the commercial world will either recognize or appreciate.  Some of the practical things I liked in the book were checklists you can give to any new team member, such as the Pre-Supervisor Checklist (p.19) to make sure someone did their homework before pushing problems up the food-chain.  (Helpful Hint:  If you want to fit in well in any engineering team and get the help you want when you need it, it’s important to make sure you’re not asking questions you could easily have solved yourself, or at least be able to demonstrate that you’ve clearly made some effort first.  I wish I would have thought of making a list like this myself working with interns, etc., as they tried to learn the ropes to make sure everyone is getting the most out of the time available in the average working day.)

There’s a lot of excellent information in this book whatever your experience level, and it’s well worth downloading and reading.  If you find it valuable, definately consider making a contribution to the author to thank him for making the book freely available online now that it’s no longer in print.

Have you ever wondered how complex ICs are really made, and how you get from raw silicon to finished chips?  I was lucky enough to spend a short but happy part of my career working at a fairly large chip fab (though as an apps engineer, nothing to do with manufacturing), but still find myself with more questions than answers on the gritty details of it all.  It was an amazing eye-opener for me to see first-hand the kind of mastery and machinery that it takes to produce finished chips, going through design, processing, testing, packaging, characterization, etc.  I think the only thing as humbling has to be seeing something like the space programs at NASA or something similar.  You can only be in awe of the level of mastery required across so many disciplines to pull something like this off.

Unfortunately, most of the technical documentation out there on this stuff is understandably written for and by people who are hopelessly above my pay grade, and I don’t understand a fraction of it (and I’m happy to admit it!).  If you’re really curious about getting an accessible look into chip design without the need for 10 years of training in semiconductor physics, though, Demystifying Chipmaking by Yanda, Heynes and Miller (published by Newnes) is an unusually accessible introduction to the topic.  (You can even get the first three chapters free in a preview off Amazon if you have a Kindle or download the Kindle SW.)  It’s an old book, but it’s still relevant today since it’s focused on CMOS, and even if they only talk a bit about the <100nm processes that are common today, the basics still apply.  Have a look at the free chapters, and see if the rest interests you!

Admittedly, Interconnecting Smart Objects with IP [ISBN: 0123751659] by Jean-Philippe Vasseur and Adam Dunkels (of lwip and Contiki fame) deservedly made the rounds a while back, so we might seem a bit late on the draw pointing it out again here.  But while I haven’t been doing anything with wireless lately myself — that’s much more the domain of the always knowledgable Akiba over at Freaklabs, who I’m always happy to defer to – I pulled this book out again this month for something else.  It goes into a lot of valuable detail on what it takes to implement a complete wireless sensor network infrastructure and it’s well worth the investment if you have any interest in WSNs, but an unexpected bonus for me the first time I read the book is that it also gives you an excellent overview of all the little pieces that fit into IP-based networking of any type … and there are a lot of pieces in that puzzle!  If you’re interested in getting started with IPv4 or IPv6 and Ethernet, there is a lot of information out there, but I was surprised to find Vasseur and Dunkels’ summary one of the most readable and accessible introductions that I’ve encountered, giving you a good understanding of the glue that holds everything together.  Trying to add wireless OR wired network connectivity to your next great idea of project?  You could do worse than spend an evening with this book and a good highlighter.

Alright … I admit the title sounds repulsive and makes you want to click away, but being someone interested in design as well as engineering, I sometimes look at sites like smashingmagazine just to see if there’s anything worth procrastinating over for a few minutes.  The article above is well worth a read.

Why am I posting this here on Adafruit under EEBookshelf, though?  Because I see a lot of questions about how to run your own kit business, and in my opinion — and I know Phil and Limor share it — good, precise, expert information is the best marketing you can ever  provide.  Give people the information they want in a regular, concise and accessible way, and as long as your products are aligned with people’s needs and expectations, the customers will inevitably come to you.  Good information is, in my opinion, the key to running a successful business, though it’s obviously more complicated than that.  Why was I an Adafruit customer long before I was an Adafruit employee?  Because they also treat their customers, their employees and their business partners fairly, and they play by the unspoken rules that reflect the best of what open source hardware should be.

Working in the kit business is exceptionally hard.  The support, shipping, sourcing and stock maintenance, site development, and a lot of other S’s make for long days, but if you’re serious about getting started, the best thing you can do is focus on a specific area that isn’t being treated well, and provide the kind of expert information that makes people want to come to you.  There are some huge gaps in knowledge out there, and people are thirsty for information … the best way to succeed online is to feed that need in a regular, readable format.  This article from smashing makes some good points about getting started doing it well from day one.

If you’ve ever had any questions about how to efficiently add CRC (Cyclical Redundancy Check) to your code, this PDF from the author behind the excellent Hacker’s Delight (Henry S. Warren) is a great start.  If you’re interested in writing efficient code, the rest of the site is worth a browse as well: http://www.hackersdelight.org/

I’ve been having a lot of noise problems lately, both with boards and with equipment doing testing in the lab.  As a result, I spent a bit of time looking around at some solutions to help reduce the noise on existing boards (basically filtering since the noisy board itself is out of my control), and came across a good app-note from Freescale on noise reduction techniques.  A lot of this is focused on PCB design, and much of the information is available from other sources, but if you’re serious about designing good PCBs, it’s worth a read and is more accessible than some other documents out there on the subject.  A lot of noise reduction comes down to good grounding, and unfortunately it’s not something that’s always done half as well as it could be (and I’ve been as guilty of this as anyone, though I’m making a conscious effort to consistently improve).  High frequency return paths need to be kept in mind while routing and laying out your PCBs — not after the fact — since you can’t do much about it when you find out you have noise problems and poor performance once the PCBs come back and get assembled.  See AN1705: Noise Reduction Techniques for Microcontroller-Based Systems for some good tips and suggestions.

While this is neither and app-note nor a book, I’ve been interested in anti-aliasing for quite some times since A.) UI design is just kind of a fetish of mine, and B.) There’s almost no useful information out there on this stuff in a form that’s appropriate to low-cost embedded systems.  Which is where this weeks EEBookshelf entry comes in: a very old article (think Quick Basic, ya … that thing you used back in High School or earlier) explaining the basics of anti-aliasing pixels.  While the text is obscenely small, the explanation is very clear, and it’s easy to transfer this to your own firmware in C or whatever else.  Now to work this into some of my own projects and see how far I can stretch the 72MHz on the LPC1343 and the few hundred KBs I have left! See QB EXpress: Issue #22 for this article from Eclipzer.  My advice … if you find this useful save it to a PDF somewhere special.

Recently picked up an oscilloscope from Adafruit, or wondering what you might use one for if you did have one at your disposal?  Tektronix ‘XYZs of Oscilloscopes‘* gives a great introduction to the basics of scopes, and the content is all pretty much universal.  Having a scope opens up a world of debugging and learning opportunities (seeing is believing!), but the learning curve can be a bit steep if it’s your first time in front of one.  Know any other good tutorials to help people get started?  Feel free to post them in the comments below!

*Note: Registration is required to download any of the primers and guides from Tek, but it’s all free and there really is some good information in the different guides.

Looking for a poor-man’s capacitive touch sensor using only the ADC on your MCU and a couple discrete components?  NXP shows how it can be done in AN11023: Capacitive Touch Sensing using the LPC11xx (here for .zip file with code).  (Note: While this app note is aimed at the ARM Cortex M0 LPC11xx series of chips, the information is easily transferable to any other MCU.)

Analog Devices (who have a lot of great app notes locked up in their stable) have made available in PDF format enough good information and reading material to keep you busy for the rest of the winter while you wait for warm enough weather that you want to step outside again.  Their Linear Circuit Design Handbook has a lot of excellent material, and can also be ordered in printed format if you’re still a fan of a good old highlighter and notes in the margin like me.